The Fox is Black
Desktop Wallpaper Project
The lovely folks over at http://www.thefoxisblack.com/category/the-desktop-wallpaper-project/ have been releasing a treasure trove of awesome desktop designs as a part of the Desktop Wallpaper Project. I found the webpage to be a little slow to load and there is unfortunately no way to download all backgrounds as a bundle. I wrote this little script to grab all the background in 1400x900.
You can find the entire dump at this link.